Genuine or aftermarket spare parts: how to choose

When a part fails you usually get two options: the original part from the car maker, or an aftermarket alternative. The right choice depends on the part, the car and your budget.

What the words mean

• Genuine parts are made to the car maker's specification and carry its branding.
• Quality aftermarket parts come from established manufacturers and are designed to fit and perform like the original.
• Low-grade copies imitate the look of a part but not its materials or tolerances. These are the ones to avoid.

When genuine is worth it

Choose genuine for parts where a failure is dangerous or very expensive: airbags, brake components, engine management sensors and timing parts. Many of these also need exact specification to work with the car's computer.

When a quality alternative is sensible

Filters, belts, wipers, bulbs, many suspension parts and cosmetic panels are commonly available in good aftermarket versions at a lower price.

How to avoid buying the wrong part

1. Give the seller your chassis number so the part is matched to your exact car.
2. Ask them to say clearly whether it is genuine or an alternative.
3. Keep the old part, or a photo of it, to compare when the new one arrives.
4. Buy from a supplier who will take back a part that does not fit.

If you are not sure what your car needs, a diagnostic scan first will tell you whether you are replacing the right part.